We are having a rather strange problem with our new exchange 2010 server.
at least once a week it seems to randomly stop sending out emails with a 421 4.2.1 and a 451 4.4.0 error.
These are email domains that we frequently send a recieve from without any issues.
we can still recieve emails, but any mails sent to an external address just stack up for a few hours with the about errors. they will eventually send however.
We have tried recreating the send connectors, restarting the transport services as recomended but it seems to be happening more frequently.
Can anyone suggest more options?
its a MS Server 2008 and exchange 2010, new to this version so "idiot" guides would be great.
i have attached a screen shot of the error messages.